Background Pyogenic arthritis ( PA) is still a problematic arthritic disease that requires hospitalization. Objective To study the epidemiological characteristics and predictors of treatment outcomes for Thai patients hospitalized with PA. Materials and methods The nationwide hospital database from the 2010 fiscal year was analyzed. Patients 18 years of age onward, who had primary diagnosis of pyogenic arthritis, were included in this study. Results There were a total of 6242 PA admissions during 2010. It was ranked third among hospitalized musculoskeletal patients after osteoarthritis ( OA) and gouty arthritis. The estimated prevalence of PA was 13.5 per 100 000 adult population. Geographic distributions of PA was related to the population density of each region; however it seemed more frequent in the northern and northeastern regions of Thailand. The prevalence increased with age, 3.6 and 43.6 per 100 000 in young adults and the elderly, respectively. Among the 2877 co-morbidities coded, diabetes was the most common, followed by crystal-induced arthritis, existing other foci of infections (urinary tract infection, skin and soft tissue infections and pneumonia) and pre-existing chronic joint diseases ( OA,rheumatoid arthritis), respectively. Overall hospital mortality rate was 2.6%. Poorer outcomes were found among patients with chronic liver disease and other existing foci of infections. Conclusions The prevalence of hospitalized PA is still modest in Thailand, showing the highest prevalence in the advanced age group. Diabetes was the most commonly co-morbidity found; however, poorer outcomes were noted among patients with chronic liver disease and existing multiple sites of infections. [ABSTRACT FROM AUTHOR]